Conventional software utilities, such as the commonly used ping utility, are useful tools for determining whether a remote interface is active. These tools typically require a user to enter a unique identifier, such as a particular internet protocol (IP) address, of a remote host in order to test the status of a corresponding network interface. For example, the ping protocol tests status of a remote interface by sending an Internet Control Message Protocol (ICMP) echo request packet to a specific IP address assigned to that interface. If an echo reply packet is not received within a defined time period, connectivity to that interface is assumed to be down.
In general, utilizing conventional ping to test the status of a particular network interface of a remote network device requires network reachability between the testing device and the remote network interface. For example, by specifying a global, publicly-reachable IP address of a particular interface of a remote device, an administrator may direct ping to that interface of the target device. When a private IP addresses is assigned to a network interface, such an interface can generally only be tested from a network device having network reachability to the private IP address, i.e., a network device within the same private network. Network interfaces having link-local IP addresses can generally only be tested using an interface connected to the same network link, i.e., from directly connected devices.
In this sense, global IP addresses may be preferable in terms of testability via software utilities such as conventional ping. However, assignment of global IP addresses to each individual network interface may be undesirable for many reasons. For example, assigning known IP addresses to each individual interface exposes the device to interface-specific network attacks, such as packet-flooding of a particular interface. Furthermore, assigning and managing individual IP addresses for each interface of each network device within a network may increase operational expenses.
For these reasons, network administrators may elect to forego assignment of an individual publicly known identifier, such as an IP address, to each network interface. Although this approach avoids the security risks and operational expenses associated with assignment of IP address to each interface, the network administrators are unable to use conventional testing utilities, such as ping, to test the status of particular network interfaces.